Carbazolylmethane dye salts as sensitizers for photoconductor compositions

ABSTRACT

Tris(9-alkylcarbazol-3-y1)methane dyes and tris(9-arylcarbazol3-y1)methane dyes enhance the sensitization of photoconductive layers containing various photoconductors. These materials are particularly useful in elements used in electrophotographic processes.

United States Patent Holstead Mar. 7, 1972 [54] CARBAZOLYLMETHANE DYE SALTS 3,503,740 3/ I970 De Seims et a]. ..96/l.5

As SENSITIZERS FOR n V. it is H PHOTOCONDUCTOR COMPOSITIONS Primary Examiner-George F. Lesmes [72] Inventor: Colin llolstead, 37 Abbotts Road Abbotts Asa-5mm m C. Cooper Langley, Walford, England Attorney-William n. J. Kline, James R. Frederick and Fred 221 Filed: Oct. 22,1969 211 A pi. No.: 868,600

57] ABSTRACT [52] U-S-Cl. ..96/l.6, 96/].5, 96/ 1.7, T|is(9 a|kylcarbazo| 3 yl)mcthane d and i 9 260/215 bazol-3-yl)methane dyes enhance the sensitization of [51] Int. Cl .303 5/06,G03g 5/08 photoconducfive layers containing various photoconductora [58] FieldoISeamh ..96/l.5-l.7; These m are ni l -ly f in elements used in 260/315 electrophotographic processes.

[56] References Cited 15 Claims, N0 Drawings UNITED STATES PATENTS m CARBAZOLYLMETHANE DYE SALTS AS SENSITIZERS FOR PHOTOCONDUCT OR COMPOSITIONS This invention relates to electrophotography, and in particular to novel sensitized photoconductive compositions and elements having coated thereon such compositions.

The process of xerography, as disclosed by Carlson in US. Pat. No. 2,297,691, employs an electrophotographic element comprising a support material bearing a coating of a normally insulating material whose electrical resistance varies with the amount of incident actinic radiation it receives during an imagewise exposure. The element, commonly termed a photoconductive element, is first given a uniform surface charge, generally in the dark after a suitable period of dark adaptation. It is then exposed to a pattern of actinic radiation which has the effect of differentially reducing the potential of the surface charge in accordance with the relative energy contained in various parts of the radiation pattern. The differential surface charge or electrostatic latent image remaining on the electrophotographic element is then made visible by contacting the surface with a suitable electroscopic marking material. Such marking material or toner, whether contained in an insulating liquid or on a dry carrier, can be deposited on the exposed surface in accordance with either the charge pattern or the absence of charge pattern as desired. The deposited marking material may then be either permanently fixed to the surface of the sensitive element by known means such as heat, pressure, solvent vapor, or the like, or transferred to a second element to which it may similarly be fixed. Likewise, the electrostatic latent image can be transferred to a second element and developed there.

Various photoconductive insulating materials have been employed in the manufacture of electrophotographic elements. For example, vapors of selenium and vapors of selenium alloys deposited on a suitable support and particles of photoconductive zinc oxide held in a resinous, film-forming binder have found wide application in present-day document copying applications.

Since the introduction of electrophotography, a great many organic compounds have also been screened for their photoconductive properties. As a result, a very large number of organic compounds are known to possess some degree of photoconductivity. Many organic compounds have revealed a useful level of photoconduction and have been incorporated into photoconductive compositions. Optically clear organic photoconductor-containing elements having desirable electrophotographic properties can be especially useful in electrophotography. Such electrophotographic elements may be exposed through a transparent base if desired, thereby providing unusual flexibility in equipment design. Such compositions, when coated as a film or layer on a suitable support also yield an element which is reusable; that is, it can be used to form subsequent images after residual toner from prior images has been removed by transfer and/or cleaning.

Although some of the organic photoconductors comprising the materials described are inherently light sensitive, their degree of sensitivity is usually low and in the short wavelength portion of the spectrum so that it is common practice to add materials to increase the speed and to shift the sensitivity toward the longer wavelength portion of the visible spectrum. lncreasing the speed and shifting the sensitivity of such systems into the visible region of the spectrum has several advantages: it makes available inexpensive and convenient light sources such as incandescent lamps; it reduces exposure time; it makes possible the recording of a wide range of colors in proper tonal relationship, and allows projection printing through various optical systems. By increasing the speed through the use of sensitizers, photoconductors which would otherwise have been unsatisfactory are useful in processes where high speeds are required such as document copying.

It is therefore an object of this invention to provide novel sensitized photoconductive elements.

It is another object of this invention to provide novel sensitized photoconductive compositions.

It is a further object of this invention to provide a process for using novel sensitized photoconductive elements.

These and other objects are accomplished by using either a tris(9-alkyl carbazol-3-yl)methane dye or a tris(9-arylcarbazol-3-yl)methane dye as a sensitizer for a photoconductive composition. The carbazole nucleus of hese dyes can be further substituted by additional groups such as alkoxy, aryloxy, alkyl, acyl, halogen, etc. The use of photoconductive compositions containing the sensitizing dyes of this invention in electrophotographic elements increases the speed of such elements when exposed in an electrophotographic process compared to the speeds attainable when the sensitizer is absent. When the sensitizer is not present in the photoconductive layer, the resultant speed of the layer is frequently not fast enough to produce a developable electrostatic latent image.

The preferred sensitizing dyes described herein have the following formula:

wherein:

R represents any of the following 1. an aliphatic group having one to 18 carbon atoms e.g., methyl, ethyl, propyl, butyl, isobutyl, octyl, dodecyl, etc. including a substituted alkyl group having one to 18 carbon atoms such as a. alkoxyalkyl e.g., ethoxypropyl, methoxybutyl, propoxymethyl, etc., I

b. aryloxyalkyl e.g., phenoxyethyl, naphthoxymethyl,

phenoxypentyl, etc.,

c. aminoalkyl, e.g.,

aminopropyl, etc.,

d. hydroxyalkyl e.g., hydroxypropyl, hydroxyoctyl, etc.,

e. aralkyl e.g., benzyl, phenethyl, etc.,

f. alkylaminoalkyl e.g., methylaminopropyl,

methylaminoethyl, etc., and also including dialkylaminoalkyl e.g., diethylaminoethyl, dimethylaminopropyl, propylaminooctyl, etc.,

arylaminoalkyl, e.g., phenylaminoalkyl, diphenylaminoalkyl, N-phenyl-N-ethylaminopentyl N-phenyl- N-ethylaminohexyl, naphthylaminomethyl, etc., h. nitroalkyl, e.g., nitrobutyl, nitroethyl, nitropentyl, etc., i. cyanoalkyl, e.g., cyanopropyl, cyanobuty], cyanoethyl,

etc., j haloalkyl, e.g., chloromethyl, bromopentyl, chlorooctyl, etc., k. alkyl substituted with an acyl group having the formula aminobutyl, aminoethyl,

wherein R is hydroxy, hydrogen, aryl, e.g., phenyl, naphthyl, etc., lower alkyl having one to 8 carbon atoms e.g., methyl, ethyl, propyl, etc., amino including substituted amino e.g., diloweralkylamino, lower alkoxy having one to 8 carbon atoms e.g., butoxy, methoxy, etc., aryloxy e.g., phenoxy, naphthoxy, etc.; or

2. an aryl group, e.g., phenyl, naphthyl anthryl, tluorenyl,

etc., including a substituted aryl group such as e. biphenylyl,

aminophenyl, aminonaphthyl,

f. alkylaminoaryl, e.g., methylaminophenyl,

methylaminonaphthyl, etc. and also including dialkylarninoaryl, e.g., diethylaminophenyl,

dipropylaminophenyl, etc.,

g. arylaminoaryl, e.g., phenylaminophenyl, diphenylaminophenyl, N-phenyl-N-ethylaminophenyl, naphthylaminophenyl, etc.,

h. nitroaryl e.g., nitrophenyl, nitronaphthyl, nitroanthryl,

etc.,

i. cyanoaryl, e.g., cyanophenyl, cyanonaphthyl,

cyanoanthryl, etc. j. haloaryl, e. g., chlorophenyl, bromophenyl,

chloronaphthyl, etc., k. aryl substituted with an acyl group having the formula wherein R is hydroxy, hydrogen, aryl, e.g., phenyl, naphthyl, etc., amino including substituted amino, e.g., diloweralkylamino, lower alkoxy having one to 8 carbon atoms, e.g., butoxy, methoxy, etc., aryloxy, e.g., phenoxy, naphthoxy, etc., lower alkyl having one to 8 carbonatoms, e.g., methyl, ethyl, propyl, butyl, etc.,

1. alkaryl, e.g., tolyl, ethylphenyl, propyl, naphthyl, etc.;

R represents any of the following:

1. an alkoxy group having one to 18 carbon atoms, e.g.,

methoxy, ethoxy, propoxy, butoxy, etc.;

2. an aryloxy group e.g., phenoxy, naphthoxy, etc.;

3. an aliphatic group having one to 18 carbon atoms e.g., methyl, ethyl, propyl, butyl, isobutyl, octyl, dodecyl, etc., including a substituted alkyl group having one to 18 car bon atoms such as a. alkoxyalkyl e.g., ethoxypropyl, methoxybutyl, propoxymethyl, etc.,

aryloxyalkyl e.g., phenoxyethyl,

phenoxypentyl, etc.,

c. aminoalkyl, e.g., aminobutyl, aminoethyl, aminopropyl,

etc.,

(I. hydroxyalkyl e.g., hydroxypropyl, hydroxyoctyl, etc.,

e. aralkyl e.g., benzyl, phenethyl, etc.,

f. alkylaminoalkyl e.g., methylaminopropyl,

methylaminoethyl, etc., and also including dialkylaminoalkyl e.g., diethylaminoethyl, dimethylaminopropyl, propylaminooctyl, etc.,

g. arylaminoalkyl, e.g., phenylaminoalkyl, diphenylaminoalkyl, N-phenyl-N-ethylaminopentyl, N-phenyl-N-ethylaminohexyl, naphthylaminomethyl, etc.,

h. nitroalkyl, e.g., nitrobutyl, nitroethyl, nitropentyl, etc.,

i. cyanoalkyl, e.g., ,cyanopropyl, cyanobutyl, cyanoethyl, etc.,

j. haloalkyl, e.g., chloromethyl, bromopentyl, chlorooctyl, etc.,

k. alkyl substituted with an acyl group having the formula wherein R is hydroxy, hydrogen, aryl, e.g., phenyl, naphthyl, etc., lower alkyl having one to 8 carbon atoms e.g., methyl, ethyl, propyl, etc., amino including substituted amino e.g., diloweralkylamino, Ioweralkoxy having one to 8 carbon atoms e.g., butoxy, methoxy, etc., aryloxy e.g., phenoxy. naphthoxy, etc.;

4. hydrogen;

b. naphthoxymethyl,

S. substituted acyl such as those having the formula wherein R,, is hydroxy, halogen, e.g., chlorine, bromine, etc., hydrogen, aryl e.g., phenyl, naphthyl, etc., amino including substituted amino e.g., diloweralkylamino, lower alkoxy having one to 8 carbon atoms e.g., butoxy, methoxy, etc., aryloxy e.g., phenoxy, naphthoxy, etc., alkyl e.g., methyl, ethyl, propyl, etc.;

6. halogen such as chlorine, bromine, fluorine, or iodine;

and

X represents an acid anion such as a halide e.g., chloride, bromide, fluoride, iodide, perchlorate, tetrafluoroborate, sulfamate, thiocyanate, p-toluenesulfonate, methyl sulfate, etc.

Typical dyes which belong to the herein described general class of sensitizing compounds include the following:

TABLE I I. Tris( 9-methylcarbazol-3-yl)methane dye II. Tris(9-methyl-6-methoxycarbazol-3-yl)methane dye III. Tris(9-methyl-6-phenoxycarbazol-B-yl)methane dye IV. Tris(6,9-dimethylcarbazol-3-yl)methane dye V. Tris(6-acetyl-9-methylcarbazol-3-yl)methane dye VI. Tris(6-chloro-9-methylcarbazol-3-yl)methane dye VII. Tris(9-ethylcarbazol-3-yl)methane dye VIII. Tris(9-ethyl-6-methoxycarbazol-3-yl )methane dye IX. Tris(9-ethyl-6-phenoxycarbazol-3-yl )methane dye X. Tris( 6,9-diethylcarbazol-3-yl)methane dye XI. Tris(6-acetyl-9-ethylcarbazol-3-yl)methane dye XII. Tris( 6-chloro-9-ethylcarbazol-3-yl)methane dye Xlll. Tris(9-phenylcarbazol-3-yl)methane dye XIV. Tris(9-phenyl--methoxycarbazol-3-yl)methane dye XV. Tris(9-phenyl-6-phenoxycarbazol-3-yl)methane dye XVI. Tris(6-acetyl-9-phenylcarbazol-3-yl)methane dye XVII. Tris( 6-chloro-9-phenylcarbazol-3-yl)methane dye XVIII. Tris(6-methyl-9-phenylcarbazol-3-yl)methane dye Electrophotographic elements of the invention can be prepared with any photoconductive compound and the sensitizers of this invention in the usual manner, i.e., by blending a dispersion or solution of the photoconductive compound together with a binder, when necessary or desirable, and coating or forming a self-supporting layer with the photoconductive composition. Generally, a suitable amount of the sensitiz ing compound is mixed with the photoconductive coating composition so that, after thorough mixing, the sensitizing compound is uniformly distributed throughout the desired layer of the coated element. The amount of sensitizer that can be added to a photoconductor-incorporating layer to give effective increases in speed can vary widely. The optimum concentration in any given case will vary with the specific photoconductor and sensitizing compound used. In general, substantial speed gains can be obtained where an appropriate sensitizer is added in a concentration range from about 0.0001 to about 30 percent by weight of the film-forming coating composition. Normally, a sensitizer is added to the coating composition in an amount of from about 0.005 to about 5.0 percent by weight of the total coating composition.

The sensitizers of this invention improve the electrical speeds of compositions containing a wide variety of photoconwherein Z represents a mononuclear or polynuclear divalent aromatic radical, either fused or linear e.g., phenyl, naphthyl, biphenyl, binaphthyl, etc.), or a substituted divalent aromatic radical of these types wherein said substituent can comprise a member such as an acyl group having from one to about six carbon atoms (e.g., acetyl, propionyl, butyryl, etc.), an alkyl group having from one to about six carbon atoms (e.g., methyl, ethyl, propyl, butyl, etc.), an alkoxy group having from one to about six carbon atoms (e.g. methoxy, ethoxy, propoxy, pentoxy, etc.), or a nitro group; Z represents a mononuclear or polynuclear monovalent or polynuclear monovalent aromatic radical, either fused or linear (e.g., phenyl, naphthyl, biphenyl, etc.); or a substituted monovalent aromatic radical wherein said substituent can comprise a member, such as an acyl group having from one to about six carbon atoms (e.g., acetyl, propionyl, butyryl, etc.), an alkyl group having from one to about six carbon atoms (e.g., methyl, ethyl, propyl, butyl, etc.), an alkoxy group having from one to about six carbon atoms (e.g., methoxy, propoxy, pentoxy, etc.) or a nitro group; O can represent a hydrogen atom or an aromatic amino group, such as Z'NH; b represents an integer from one to about 12, and L represents a hydrogen atom, a mononuclear or polynuclear aromatic radical, either fused or linear (e.g., phenyl, naphthyl, biphenyl, etc.), a substituted aromatic radical wherein said substituent comprises an alkyl group, an alkoxy group, an acyl group, or a nitro group, or a poly(4'-vinylphenyl) group which is bonded to the nitrogen atom by a carbon atom of the phenyl group, these materials being more fully described in U.S. Pat. No. 3,265,496.

C. Polyarylalkane photoconductors including leuco bases of diaryl or triarylmethane dye salts, l,l,l-triarylalkanes wherein the alkane moiety has at least two carbon atoms and tetraarylmethanes having an amino group substituted in at least one of the aryl nuclei attached to the alkane and methane moieties of the latter two classes of photoconductors which are nonleuco base materials; and also other polyarylalkanes included by the formula:

' wherein each of D, E and G is an aryl group and J is a wherein each R can be an alkyl group typically having one to eight carbon atoms, a hydrogen atom, an aryl group, or together the necessary atoms to form a heterocyclic amino group typically having five to six atoms in the ring such as morpholino, pyridyl, pyrry], etc.; at least one of D, E and G preferably being a p-dialkyl-aminophenyl group, when J is an alkyl group, such an alkyl group more generally has one to seven carbon atoms, these materials being more fully described in U.S. Pat. No. 3,274,000, French Pat. No. 1,383,461 and in U.S. Ser. No. 627,857 filed Apr. 3, 1967 by Seus and Goldman.

D. Photoconductors comprising 4-diarylamino substituted chalcones having the formula:

wherein R and R are each phenyl radicals including substituted phenyl radicals, R preferably having the formula:

wherein R and R are each aryl radicals, aliphatic residues of one to 12 carbon atoms such as alkyl radicals preferably having one to four carbon atoms, or hydrogen; particularly advantageous results being obtained when R, is a phenyl radical including a substituted phenyl radical and where R is diphenylaminophenyl, dimethylaminophenyl or phenyl, these materials being more fully described in Fox Application U.S. Ser. No. 613,846, now U.S. Pat. No. 3,526,501.

E. Nonionic cycloheptenyl compounds which may be substituted with substituents such as:

1. an aryl radical including substituted as well as unsubstituted aryl radicals,

2. a hydroxy radical,

3. an azido radical,

4. a heterocyclic radical having five to six atoms in the heterocyclic nucleus and at least one hetero nitrogen atom, and including substituted and unsubstituted heterocyclic radicals, and

5. an oxygen linked cycloheptenyl moiety.

The substitution on the cycloheptenyl nucleus occurs at an unsaturated carbon atom when the cycloheptenyl moiety is a conjugated triene with no aromatic structure fused thereto.

, However, if there is at least one aromatic structure fused to the cycloheptenyl moiety, then the substituents are attached to a saturated carbon atom. Additional photoconductors within this class are included in one of the following formulas:

af Ru f Rio I n where E and G can be either:

1. a phenyl radical,

2. a naphthyl radical,

3. a heterocyclic radical having five to six atoms in the heterocyclic nucleus and at least one hetero nitrogen atom,

4. a hydroxyl radical, or

5. an oxygen containing radical having a structure such that the resultant cycloheptenyl compound is a symmetrical ether;

D can be any of the substituents defined for E and G above and is attached to a carbon atom in the cycloheptenyl nucleus having a double bond; (R and R (R and R (R and R and (R and R are together the necessary atoms to complete a benzene ring fused to the cycloheptenyl nucleus; these compounds being more fully described in U.S. Ser. No. 654,091 filed July 18, 1967, now U.S. Pat. No. 3,533,786.

F. Compounds containing an nucleus including:

1. unsubstituted and substituted N,N-bicarbazyls containing the substituents in either or both carbazolyl nuclei such as:

a. an alkyl radical including a substituted alkyl radical such as a haloalkyl or an alkoxyalkyl radical,

b. a phenyl radical including a substituted phenyl radical such as a naphthyl, an aminophenyl or a hydroxyphenyl radical,

c. a halogen atom,

d. an amino radical including substituted as well as unsubstituted amino radicals such as an alkylamino or a phenylalkylamino radical,

e. an alkoxy radical, f. a hydroxyl radical, g. a cyano radical, h. a heterocyclic radical such as a pyrazolyl carbazolyl or a pyridyl radical; or

2. tetra-substituted hydrazines containing substituents which are substituted or unsubstituted phenyl radicals, or heterocyclic radicals having five to six atoms in the hetero nucleus, suitable results being obtained when all four substituents are not unsubstituted phenyl radicals, i.e., if at least one substituent is a substituted phenyl radical or a heterocyclic radical having five to six atoms in the hetero nucleus. Other tetra-substituted hydrazines include those having the following formula:

N N E1 J1 wherein D,, E G and J are each either:

a. a substituted phenyl radical such as a naphthyl radical, an alkyl phenyl radical, a halophenyl radical, a hydroxyphenyl radical, a haloalkylphenyl radical or a hydroxyalkylphenyl radical, or b. a heterocyclic radical such as an imidazolyl radical, a furyl radical, or a pyrazolyl radical. In addition J and E can also be c. an unsubstituted phenyl radical. Especially preferred are those tetra-substituted hydrazines wherein both D, and G, are either substituted phenyl radicals or heterocyclic radicals. These compounds are more fully described in U.S. Ser. No. 673,962 filed Oct. 9, 1967, now U.S. Pat. No. 3,542,546.

G. Organic compounds having a 3,3'-bis-aryl-2-pyrazoline nucleus which is substituted in either five-member ring with the same or different substituents. The one and five positions on both pyrazoline rings can be substituted by an aryl moiety including unsubstituted as well as substituted aryl substituents such as alkoxyaryl, alkaryl, alkaminoaryl, carboxyaryl, hydroxyaryl and haloaryl. The 4-position can contain hydrogen or unsubstituted as well as substituted alkyl and aryl radicals such as alkoxyaryl, alkaryl, alkaminoaryl, haloaryl, hydroxyaryl, alkoxyalkyl, aminoalkyl, carboxyaryl, hydroxyalkyl and haloalkyl. Other photoconductors in this class are represented by the following structure:

wherein:

D D;,', J 3 and J can be either a phenyl radical includinga substituted phenyl radical such as a tolyl radical or a naphthyl radical including a substituted naphthyl radical,

E E (3;, 0;, L and L can be any of the substituents set forth above and in addition can be either a hydrogen atom or an alkyl radical containing one to eight carbon atoms. These organic photoconductors are more fully described in U.S. Ser. No. 664,642 filed Aug. 31, 1967, now U.S. Pat. No. 3,527,602.

H. Triarylamines in which at least one of the aryl radicals is substituted by either a vinyl radical or a vinylene radical having at least one active hydrogen-containing group. The phrase vinylene radical" includes substituted as well as unsubstituted vinylene radicals and also includes those radicals having at least one and as many as three repeating units of vinylene groups such as -(CH CH); wherein n is aninteger of from one to three. Groups which contain active hydrogen are well known in the art, the definition of this term being set forth in several textbooks such as Advanced Organic Chemistry, R. C. Fuson, pp. 154-157, John Wiley & Sons, 1950. The term active hydrogen-containing group as used herein includes those compounds encompassed by the discussion in the textbook cited above and in addition includes those compounds which contain groups which are hydrolyzable to active hydrogen-containing groups. Typical active hydrogen-containing groups substituted on the vinylene radical of the triarylamine include:

1. carboxy radicals,

2. hydroxy radicals,

3. ethynyl radicals,

4. ester radicals (e.g.,

wherein R, is alkyl or aryl) including cyclic ester radicals (e.g.,

wherein R. is a cyclic alkylene radical connected to a vinylene combination such as is found in coumarin derivatives),

5. carboxylic acid anhydride radicals,

6. semicarbazono radicals,

7. cyano radicals,

8. acyl halide radicals (e.g.,

0 JLol etc.), and

9. amido radicals (e.g.,

wherein R is a hydrogen atom, an alkyl group or an aryl group).

Other active hydrogen-containing groups include substituted and unsubstituted alkylidyne oximido radicals. Photoconductors included in this class can be represented by the following structure:

wherein:

1. Ar, and Ar: are each a phenyl radical including a substituted phenyl radical such as a halophenyl radical, an alkyl phenyl radical or an aminophenyl radical,

2. Ar is an arylene radical including a substituted arylene radical such as a phenylene radical or a naphthylene radical,

3. R and R are each hydrogen, a phenyl radical including a substituted phenyl radical or a lower alkyl radical preferably having one to eight carbon atoms,

4. X is either:

a. an active hydrogen-containing group such as a carboxy radical, an acyl halide radical, an amido radical, a carboxylic acid anhydride radical, an ester radical, a cyano radical, a hydroxy radical, a semicarbazono radical, an ethynyl radical, or a methylidyne oximido radical, or

b. hydrogen, provided that when X is hydrogen 11. and R are also hydrogen, and 5. n is an integer of one to three.

The arylene nucleus can be substituted in any position by the vinyl or vinylene moiety. However, when Ar is phenylene, particularly good results are obtained if the substitution occurs in the para position. These materials are more fully described in US. Ser. No. 706,800 filed Feb. 20, 1968.

I. Triarylamines in which at least one of the aryl radicals is substituted by an active hydrogen-containing group. The term active hydrogen-containing group has the same meaning as set forth above and again includes those compounds encompassed by the discussion in the textbook and additionally includes those compounds which contain groups which are hydrolyzable to active hydrogen-containing groups. Typical active hydrogen-containing groups which are substituted on an aryl radical of the triarylamine include:

1. carboxy radicals,

2. hydroxy radicals,

3. ethynyl radicals,

4. ester radicals (e.g.,

wherein R is an alkyl or an aryl group),

5. lower alkylene hydroxy radicals (e.g., having one to eight carbon atoms), 7

6. carboxylic acid anhydride radicals,

7. lower alkylene carboxy radicals (e.g., having two to eight carbon atoms),

8. cyano radicals,

9. acyl halide radicals (e.g.,

, etc.),

10. amido radicals (e.g.,

0 R10 'l N wherein R is a hydrogen atom, an alkyl group or an aryl group),

11. lower alkylidyne oximido radicals having 1 to 8 carbon atoms including substituted alkylidyne oximido radicals (e.g.,

13. arylene carboxy radicals including substituted arylene carboxy radicals (e.g.,

wherein D and E, are phenyl or lower alkyl radicals. Photoconductors included in this class can be represented by the following structure:

wherein:

a. Ar, and Ar are each a phenyl radical including a substituted phenyl radical such as a halophenyl radical, an'

. alkyl phenyl radical or an amino phenyl radical,

b. Ar isan arylene radical including a substituted arylene radical such as a phenylene radical or a naphthylene radical, and

c. X is an active hydrogen-containing group such as a carboxy radical, an acyl halide radical, an amido radical, a carboxylic acid anhydride radical, an ester radical, a cyano radical, a semicarbazono radical, a hydroxy radical, an ethynyl radical, a methylidyne oximido radical or a phenylene carboxy radical.

These materials are more fully described in US. Ser. No. 706,780 filed Feb. 20, 1968.

J. Organometallic compounds having at least one aminoaryl substituent attached to a Group lVa or Group Va metal atom. The metallic substituents of this class of organic photoconductors are Group lVa or Group Va metals in accordance with the Periodic Table of the Elemerits (Handbook of Chemistry and Physics, 38th edition, pp. 394-) and include silicon, germanium, tin and lead from Group [Va and phosphorus, arsenic, antimony and bismuth from Group Va. These materials can be substituted'in the metallo nucleus with a wide variety of substituents'but at least one of the substituents must be an amino-aryl radical. The amino radical can be positioned anywhere on the aromatic nucleus, but best results are obtained if the aryl moiety is a phenyl radical having the amino group in the four or para position. Typical substituents attached to the metal nucleus include the followl. a hydrogen, sulfur or oxygen atom,

2. an alkyl radical,

3. an aryl radical including unsubstituted as well as substituted aryl radicals such as aminoaryl alkylaryl and haloaryl,

4. an oxygen-containing radical such as an alkoxy or aryloxy radical,

5. an amino radical including unsubstituted and substituted amino radicals such as monoand diarylamino and monoand dialkylamino radicals,

6. a heterocyclic radical, and

7. a Group lVa or Va organo metallic radical. Photoconductors included in this class can be represented by the following structures:

where E G L and Q can be:

a. a hydrogen atom, b. an aryl radical including unsubstituted as well as substituted aryl radicals such as a phenyl radical, a naphthyl radical, a dialkylamino phenyl radical, ,or a di- 1 wherein R and R can be hydrogen atoms or alkyl radicals having one to 8 carbon atoms, or

g. a heterocyclic radical having five to six atoms in the hetero nucleus including at least one nitrogen atom such as a triazolyl, a pyridyl radical, etc.,

T is an amino radical such as an alkylamino radical having one to eight carbon atoms or an arylamino radical such as a phenylarnino radical;

Are is an aromatic radical such as phenyl or naphthyl;

Ma, and Ma are the same or different Group IV metals;

M is a Group Va metal;

D can be any of the substituents set forth above for E G L and Q and in addition can be a Group IVa organometallic radical or, when taken with E, an oxygen atom or a sulfur atom;

J can be any of the substituents set forth above for E G L and Q and in addition can be when taken with E, an oxygen atom or a sulfur atom. These materials are described in US. Ser. No. 650,664 filed July 3, 1967.

K. Any other organic compound which exhibits photoconductive properties such as 9-alkylcarbazoles and 9-arylcarbazoles and also those set forth in Australian Pat. No. 248,402.

Representative organic photoconductors useful in this invention include the compounds listed below:

TABLE] diphenylamine dinaphthylamine N,N'-diphenylbenzidine N-phenyl- 1 -naphthylamine N-phenyl-Z-naphthylamine N,N'-diphenyl-p-phenylenediamine 2-carboxy-5-chloro-4 '-methoxydiphenylamine p-anilinophenol N,N'-di-2-naphthyl-p-phenylenediamine 4,4'-benzy1idene-bis-( N,N-dimethyl-m-toluidine) triphenylamine N,N ,N' ,N'-tetraphenyl-m-phenylenediamine 4-acetyltriphenylamine 4-hexanoyltriphenylamine 4-lauroyltripheny1amine 4-hexy1triphenylamine 4-dodecyltriphenylamine 4,4'-bis(diphenylamino)benzi1 4,4'-bis( diphenylamino)benzophenone po1y[N,4' -(N,N,N'-triphenylbenzidine)] polyadipyltriphenylamine polysebacyltriphenylamine polydecamethylenetriphenylamine poly-N-( 4-viny1phenyl )diphenylarnine po1y-N-( vinylphenyl )-a,a'-dinaphthylamine 4,4'-benzylidene-bis(N,N-diethyl-m-toluidine) 4',4"-diamino-4 dimethylamino-2',2"-dimethyltriphenylmethane 4 ,4 '-bis( diethylamino)-2,6-dich1oro-2 ',2 '-dimethy1- triphenylmethane 4',4 '-bis( diethylamino )-2 ,2 '-dimethyldiphenylnaphthylmethane 2,2' -dimethyl-4,4,4' -tris(dimethylamino)triphenylmetha 4' '-bis( diethylamino )-4-dimethylamino-2 ,2 '-dimethyltriphenylmethane 4',4 '-bis( diethylamino)-2-chloro-2 ,2 '-dimethyl-4- dimethylaminotriphenylmethane 4' ,4 '-bis( diethylamino)-4-dimethylamino-2,2 ',2

trimethyltriphenylmethane 4',4 '-bis( dimethylamino )-2-chlor0-2' ,2 -dimethyltriphenylmethane 4',4 '-bis( dimethylamino)-2 ,2 '-dimethyl-4-methoxytriphenylmethane bis( 4-diethylamino)- l ,1 1 -triphenylethane bis(4-diethylamino )tetraphenylmethane 4 ,4 -bis( benzylethylamino )-2',2 -dimethyltriphenylmethane 4' ,4' '-bis(diethy1amino)-2' ,2 '-diethoxytriphenylmethane 4,4'-bis(dimethylamino)-1,1 1 -tripheny1ethane 1-(4-N,N-dimethylaminophenyl )-1 l-diphenylethane 4-dimethylaminotetraphenyl methane 4-diethylaminotetraphenylmethane 4,4'-bis( diphenylarnino )chalcone 4-diphenylamino-4'-dimethy1aminochalcone 4-dimethylaminoA'-diphenylaminochalcone 4,4 -bis(dimethylamino)chalcone 4,4 '-bis(diethylamino)chalcone 4-diethy1amine-4-diphenylaminocha1cone 4-diphenylaminochalcone 4-dimethylaminochalcone 4 '-diphenylaminochalcone 4'-dimethylaminochalcone bis-[ 5-( 5H-dibenzo[ a,d]cycloheptenyl ]ether 5-hydroxy-5H-dibenzo[ a,d ]cycloheptene l -{5-(SH-dibenzola,d]cyc1ohepteny1)} -4,5-dibenzoy1- l ,2,3-triazole 5-azido-SH-dibenzo[a,d lcycloheptene 1- {5-( 10,1 1-dihydro-5Hdibenzo[a,d lcycloheptenyl -4,5-

dicarbomethoxy-1,2,3-triazole 1-{ 5-( 10,1 l-dihydro-5H-dibenzo[ a,d]cyc1oheptenyl -4,5-

dibenzoyl- 1 ,2,3-triazole 4-[ 5-(51-1-dibenzo[a,dlcycloheptenyl) ]-N,N-

dimethylaniline N,N-diethyl-3-methyl-4-[ 5-( SH-dibenzola,d]cyclohepteny 1)]aniline 4-[5-(5H-dibenzo[a,d]cyc1oheptenyl)]-1- dimethylaminonaphthalene N,N-diethy1-3-methyl-4-[ 5-( 10,1 1-dihydro-5H- dibenzo[a,d ]-cyc1oheptenyl aniline 3-(4-dimethyl aminopheynl)-1,3 ,S-cycloheptatriene 3-(4-diethylamino-2methy1pheny1)-l ,3,5-cycloheptatriene 3-(4-dimethylaminonaphthyl)-1 ,3,5-cycloheptatriene N,N-diethyl-3-methyl-4-[ 5-( 5H-dibenzo[ a,d]cyclohepteny 1) ]ani1ine tetra-a-naphthylhydrazine tetra( 3-methyl-4-hydroxyphenyl )hydrazine tetra( m-hydroxyethylphenyl )hydrazine tetra( Z-methyl-S-chloroethylpheny1 )hydrazine tetra(2-methy1-5-hydroxyphenyl)hydrazine tetra( 1 -imidazo1yl)hydrazine N,N-di-a-naphthyl-N ',N '-di( 3-methyl-4-hydroxyphenyl )hydrazine N-3-furyl-N-( 2-methy1-4-hydroxyphenyl )-N ,N '-di-B- naphthylhydrazine tetra-B-naphthylhydrazine N,N '-di-B-naphthy1-N,N '-diphenylhydrazine tetra-4-tolylhydrazine N,N'-diphenyl-N,N -di( 3-methy1-4-hydroxypheny1)hydrazine N,N'-diphenyl-N,N'-di-p-chlorophenyl hydrazine v1,31 phenyltri-(2-methyl-5-hydroxyphenyl)hydrazine N,N'-bicarbazyl cyclotetrakis(3,9-carbazolylene) 6-(3-carbazolyl)-cyclotetrakis(3,9-carbazolylene) 6-( 9-carbazolyl )-cyclotetrakis( 3 ,9-carbazolylene) 3,3'-bis( 3-carbazolyl)-9,9'-bicarbazolyl 3-( 3-carbazolyl )-9-(9-carbazolyl carbazole 3-(9-carbaziolyl)-9,9-bicarbazolyl 3,3-diethyl-9,9-bicarbazolyl 3,3-diphenyl-9,9'-bicarbazolyl 3,3'-dichloro-9,9-bicarbazolyl 4,4'-bis(diethylamino)-9,9'-bicarbazolyl 3,3'-diethoxy-9,9-bicarbazolyl l, l '-dihydroxy-9 ,9'-bicarbazolyl 2,2'-dicyano-9,9-bicarbazolyl tetra(p-diethylaminophenyl)hydrazine 3,3'-bis( 1 ,5-diphenyl-2-pyrazoline) 3 ,3 '-bis( l-p-tolyl-5-phenyl-2-pyrazoline) 3,3'-bis( l ,5-[ l-naphthyl]-2-pyrazoline) 1,5-diphenyl-3-[ 3 l '-p-tolyl-5 -phenyl)-2'-pyrazolyl1 2- pyrazoline 3,3'-bis( l ,5-diphenyl-4,5-dimethyl-2-pyrazoline) 3,3 -bis( 1 ,4,5 -triphenyl-2-pyrazoline) 3,3'-bis( l ,5-di-p-tolyl-4-methoxy-2-pyrazoline) 3 ,3 '-bis( 1 ,5-diphenyl-4-dimethylamino-Z-pyrazoline) 3,3'-bis[ l ,5-diphenyl-4-(p-chlorophenyl)-2-pyrazoline] 3 ,3 -bis[ 1 ,5-diphenyl-4,5-di-( p-diethylaminophenyl)-2- pyrazoline] 3,3'-bis[ l ,5-diphenyl-4-(p-methoxyphenyl)-5-ethyl-2- pyrazoline] 3,3'-bis( l ,5-diphenyl-4-chloromethyl-Z-pyrazoline) l,5-diphenyl-4,5-dimethyl-3-[3 l -p-tolyl-4'-diethyl-5' ,5'-methylphenyl )-2-pyrazolyl]-2-pyrazoline 4-(p-diphenylaminophenyl)-3-butenl -yne p-diphenylaminostyrene ethyl p-diphenylaminocinnamate methyl p-diphenylaminocinnamate p-diphenylaminocinnamoyl chloride p-diphenylaminocinnamic acid N,N-diphenylamide p-diphenylaminocinnamic acid anhydride 3-(p-diphenylaminophenyl)-2-butenoic acid bis(p-diphenylaminobenzal)succinic acid 4-N,N-bis(p-bromophenyl)aminocinnamic acid l-( 4-diphenylamino)naphthacrylic acid p-diphenylaminocinnamic acid p-diphenylaminocinnamonitrile 7-diphenylamino coumarin p-diphenylaminophenylvinylacrylic acid p-diphenylaminobenzyl p'-diphenylaminocinnamate 7-(p-diphenylaminostyryl)coumarin p-diphenylaminocinnamyl alcohol 4-diphenylaminocinnamaldehyde semicarbazone O-p-diphenylaminocinnamoyl p-diphenylaminobenzaldehyde oxime p-diphenylaminocinnamaldehyde oxime l ,3-bis(p-diphenylaminophenyl)-2-propen-l-ol methyl p-diphenylaminobenzoate N,N-diphenylanthranilic acid 3-p-diphenylaminophenyl-l-propanol 4-acetyltriphenylamine semicarbazone ethyl 2,6-diphenyl-4-(p-diphenylaminophenyl)benzoate l-( p-diphenylaminophenyl 1 -hydroxy-3-butyne 4-hydroxymethyltriphenylamine l-(p-diphenylaminophenyl)ethanol 4-hydroxytriphenylamine 2-hydroxytriphenylamine 4-formyltriphenylamine oxime 4-acetyltriphenylamine oxime l-(p-diphenylaminophenyl)hexanol l-(p-diphenylaminophenyl)dodecanol p-diphenylaminobenzoic acid anhydride 4-cyanotriphenylamine p-diphenylamino'oenzoic acid N,N-diphenylamide p-diphenylaminobenzoic acid p-diphenylaminobenzoyl chloride photoconductive polymeric binders having fairly high dielectric strength which are good electrically insulating film-forming vehicles.

3-p-diphenylaminophenylpropionic acid 4-formyltriphenylamine semicarbazone triphenyl-p-diethylaminophenylsilane methyl-diphenyl-p-diethylaminophenylsilane triphenyl-p-diethylaminophenylgermane triphenyl-p-dimethylaminophenylstannane triphenyl-p-diethylaminophenylstannane diphenyl-di-(p-diethylaminophenyl)stannane triphenyl-p-diethylaminophenylplumbane tetra-p-diethylaminophenylplumbane phenyl-di-(p-diethylaminophenyl)phosphine bis(p-diethylaminophenyl)phosphine oxide tri-p-dimethylaminophenylarsine tri-p-diethylaminophenylarsine 2-methyl-4-dimethylaminophenylarsine oxide tri-p-diethylaminophenylbismuthine methyl-di-(p-diethylaminophenyl)arsine methyl-di-(p-diethylaminophenyl)phosphine phenyl-tri( p-diethylaminophenyl )stannane methyl-tri(p-diethylaminophenyl)stannane tetra-p-diethylaminophenylgermane diphenyl-p-diethylaminophenylsilane p-diethylaminophenylarsine tetrakis-[diphenyl-(p-diethylaminophenyl)plumbyl] methane tetrakis-[diphenyl-(p-diethylaminophenyl )stannyl1stannane bis-[phenyl-(p-diethylaminophenyl)ldibismuthine tri-(p-diethylaminophenyl )phosphine sulfide di-( p-diethylaminophenyl )thioxotin 9-methylcarbazole 9-ethylcarbazole 9-phenylcarbazole Preferred binders for use in preparing the present layers are film-forming, hydrophobic Typical of these materials are:

1. Natural resins including gelatin, cellulose ester derivatives such as alkyl esters of carboxylated cellulose, hydroxy ethyl cellulose, carboxy methyl cellulose, carboxy methyl hydroxy ethyl cellulose, etc.;

ll. Vinyl resins including a. polyvinyl esters such as a vinyl acetate resin, a

copolymer of vinyl acetate and crotonic acid, a copolymer of vinyl acetate with an ester of vinyl alcohol and a higher aliphatic carboxylic acid such as lauric acid or stearic acid, polyvinyl stearate, a copolymer of vinyl acetate and maleic acid, a poly(vinylhaloarylate) such as poly(vinyl-mbromobenzoate) or poly(vinyl-n-bromobenzoate-covinyl acetate), a terpolymer of vinyl butyral with vinyl alcohol and vinyl acetate, a terpolymer of vinyl formal with vinyl alcohol and vinyl acetate, etc.;

. vinyl chloride and vinylidene chloride polymers such as a poly(vinylchloride), a copolymer of vinyl chloride and vinyl isobutyl ether, a copolymer of vinylidene chloride and acrylonitrile, a terpolymer of vinyl chloride, vinyl acetate and vinyl alcohol, poly(vinylidene chloride) a terpolymer of vinyl chloride, vinyl acetate and maleic anhydride, a copolymer of vinyl chloride and vinyl acetate, etc.;

c. styrene polymers such as a polystyrene, a nitrated polystyrene, a copolymer of styrene and monoisobutyl maleate, a copolymer of styrene with methacrylic acid, a copolymer of styrene and butadiene, a copolymer of dimethylitaconate and styrene, polymethylstyrene, etc.;

d. methacrylic acid ester polymers such as a poly(alkylmethacrylate), etc.;

e. polyolefins such as chlorinated polyethylene,

chlorinated polypropylene, poly(isobutylene), etc.;

f. poly(vinyl acetals) such as a poly(vinyl butyral), etc.;

and

g. poly(vinyl alcohol);

Ill. Polycondensates including a. a polyester of 1,3-disulfobenzene and 2,2-bis(4- hydroxyphenyl)propane;

b. a polyester of diphenyl-p,p'-disulphonic acid and 2,2-

bis(4-hydroxyphenyl)propane;

c. a polyester of 4,4'-dicarboxyphenyl ether and 2,2-

bis(4-hydroxyphenyl)propane;

d. a polyester of 2,2-bis(4-hydroxyphenyl)-propane and fumaric acid;

e. pentaerythrite phthalate;

f. resinous terpene polybasic acid;

g. a polyester of phosphoric acid and hydroquinone;

h. polyphosphites;

i. polyester of neopentylglycol and isophthalic acid;

j. polycarbonates including polythiocarbonates such as the polycarbonate of 2,2-bis(4-hydroxypheny wwp k. polyester of isophthalic acid, 2,2-bis-4-B-hydroxyethoxy)phenyl propane and ethylene glycol;

l. polyester of terephthalic acid, 2,2-bis 4-B-hydroxyethoxy)phenyl and ethylene glycol;

m. polyester of ethylene glycol, neopentyl, glycol,

terephthalic acid and isophthalic acid;

n. polyamides; I

o. ketone resins; and

p. phenolformaldehyde resins;

IV. Silicone resins;

V. Alkyd resins including styrene-alkyd resins, siliconealkyd resins, soya-alkyd resins, etc.; and

VI. Polyamides.

VIII. Mineral waxes.

Solvents useful for preparing coating compositions with the use of the present invention can include a wide variety of organic solvents for the components of the coating composition. Typical solvents include aromatic hydrocarbons such as benzene, naphthalene,

etc., including substituted aromatic hydrocarbons such as toluene, xylene, mesitylene, etc.;

ketones such as acetone, 2-butanone, methylethylketone,

etc.;

3. halogenated aliphatic hydrocarbons such as methylene chloride, chloroform, ethylene chloride, etc.;

4. ethers including cyclic ethers such as tetrahydrofuran,

ethylether; and

5. mixtures of the above.

In preparing the coating compositions utilizing the photoconducting compounds disclosed herein useful results are obtained where the photoconductive substance is present in an amount equal to at least about 1 weight percent of the coating composition. The upper limit in the amount of photoconductive material present can be widely'varied in accordance with usual practice. It is normally required that the photoconductive material be present in an amount ranging from about 1 weight percent of the coating composition to about 99 weight percent of the coating composition. A preferred weight range for the photoconductive material in the coating composition is from about 10 weight percent to about 60 weight percent.

Coating thicknesses of the photoconductive composition on a support can vary widely. Normally, a wet coating thickness in the range of about 0.001 inch to about 0.01 inch is useful in the practice of the invention. A preferred range of coating thickness is from about 0.002 inch to about 0.006 inch before drying although such thicknesses can vary widely depending on the particular application desired for the electrophotographic element.

Suitable supporting materials for the photoconductive layers of the present invention can include any of the electrically conducting supports, for example, various conducting papers; aluminum-paper laminates; metal foils, such as aluminum foil, zinc foil, etc.; metal plates such as aluminum, copper, zinc, brass, and galvanized plates; vapor deposited metal layers such as silver, nickel or aluminum on conventional film supports such as cellulose acetate, poly(ethylene terephthalate), polystyrene and the like conducting supports.

An especially useful conducting support can be prepared by coating a transparent film support material such as poly(ethylene terephthalate) with a layer containing a semiconductor dispersed in a resin. A suitable conducting coating can be prepared from the sodium salt of a carboxyester lactone of a maleic anhydride-vinyl acetate copolymer, cuprous iodide and the like. Such conducting layers and methods for their optimum preparation and use are disclosed in US. Pat. Nos. 3,007,901, 3,245,833 and 3,267,807.

The compositions of the present invention can be employed in photoconductive elements useful in any of the well known electrophotographic processes which require photoconductive layers. One such process is the xerographic process. In a process of this type, an electrophotographic element held in the dark, is given a blanket electrostatic charge by placing it under a corona discharge to give a uniform charge to the surface of the photoconductive layer. This charge is retained by the layer owing to the substantial dark insulating property of the layer, i.e., the low conductivity of thelayer in the dark. The electrostatic charge formed on the surface of the photoconductive layer is then selectively dissipated from the surface of the layer by imagewise exposure to light by means of a conventional exposure operation such as for example, by a contact-printing technique, or by lens projection of an image, or reflex or bireflex techniques and the like, to thereby form a latent electrostatic image in the photoconductive layer. Exposing the surface in this manner forms a pattern of electrostatic charge by virtue of the fact that light energy striking the photoconductor causes the electrostatic charge in the light struck areas to be conducted away from the surface in proportion to the intensity of the illumination in a particular area.

The charge pattern produced by exposure is then developed or transferred to another surface and developed there, i.e., either the charge or uncharged areas rendered visible, by treatment witha medium comprising electrostati-cally responsive particles having optical density. The developing electrostatically responsive particles can be in the form of a dust, or powder and generally comprise a pigment ina resinous carrier called a toner. A preferred method of applying such a toner to a latent electrostatic image for solid area development is by the use of a magnetic brush. Methods of forming and using a magnetic brush toner applicator are described in the following US. Pat. Nos. 2,786,439; 2,786,440; 2,786,441; 2,811,465; 2,874,063; 2,984,163; 3,040,704; 3,117,884 and reissue Re. No. 24,779. Liquid development of the latent electrostatic image may also be used. In liquid development the developing particles are carried to the image-bearing surface in an electrically insulating liquid carrier. Methods of development of this type are widely known and have been described in the patent literature, for example, US. Pat. No. 2,297,691 and in Australian Pat. No. 212,315. In dry developing processes the most widely used method of obtaining a permanent record is achieved by selecting a developing-particle which has as one of its components a low-melting resin. Heating the powder image then causes the resin to melt or fuse into or on the element. The powder is, therefore, caused to adhere permanently to the surface of the photoconductive layer. In other cases, a transfer of the charge image or powder image formed on the photoconductive layer can be made to a second support such as paper which would then become the final print after developing and fusing or fusing respectively. Techniques of the type indicated are well known in the art and have been described in a number of US and foreign patents, such as US. Pat. NOs. 2,297,691 and 2,551,582, and in RCA Review, vol. 15 (1954) pages 469-484.

The compositions of the present invention can be used in electrophotographic elements having many structural variations. For example, the photoconductive composition can be coated in the form of single layers or multiple layers on a suitable opaque or transparent conducting support. Likewise, the layers can be contiguous or spaced having layers of insulating material or other photoconductive material between layers or overcoated or interposed between the photoconductive layer or sensitizing layer and the conducting layer. It is also possible to adjust the position of the support and the conducting layer by placing a photoconductor layer over a support and coating the exposed face of the support or the exposed or overcoated face of the photoconductor with a conducting layer. Configurations differing from those contained in the examples can be useful or even preferred for the same or different application for the electrophotographic element.

The following examples are included for a further understanding of this invention.

EXAMPLE I A composition in the form of a dope consisting of the following materials is coated at a wet thickness of 0.004 inch on a poly(ethylene terephthalate) film support having a conducting layer of the sodium salt of a carboxyester resin lactone:

Photoconductor N-methylcarbazole 0.5 g. Polymeric Binder [Vitel ll a polyester resin sold by Goodyear Tire and Rubber Company comprising poly(4,4'-

isopropylidenebisplenoxyethyl-coethylene terephthalatefl 1.5 g. Sensitizer (see Table II) 0.00] g. Solvent Dichloromethane 9.6 g.

The coating block is maintained at 90 F. until the solvent is removed. In a darkened room, the surface of the photoconductive layer so prepared is charged to a potential of about 600 volts under a corona charger. The layer is then covered with a transparent sheet bearing a pattern of opaque and light transmitting areas and exposed to the radiation from an incandescent lamp with an illumination intensity of about 75 metercandles for 12 seconds. The resulting electrostatic latent image is developed by cascading over the surface of the layer negatively charged black thermoplastic toner particles on glass bead carriers. The quality of the image reproduced using various sensitizers described herein is set forth in the following table.

TABLE II Sensitizer Image Quality 1 Good ll Good lV Good EXAMPLE 2 Example 1 is repeated using N-ethyl carbazole as the photoconductor. The quality of the images reproduced using various sensitizers is set forth in Table III.

TABLE III Sensitizer Image Quality Vll Good Vlll Good X Good EXAMPLE 3 Example 1 is repeated using triphenylamine as the photoconductor. In each instance a good reproduction is obtained.

EXAMPLE 4 Example 1 is repeated except no sensitizer is used. No developable latent electrostatic image is obtained.

The novel sensitizers described herein can be prepared by any one of several methods. One method involves reacting oxalyl chloride with the appropriate substituted carbazole in the presence of zinc chloride. Another synthesis involves reacting an appropriate di(carbazol-3-y1) ketone with a corresponding substituted carbazole in the presence of phosphorus oxychloride. A third method of preparation is to react a corresponding substituted carbazole with carbon tetrachloride in the presence of aluminum chloride. In any of the synthesis mentioned above, the reaction product contains one of the sensitizing dyes described herein together with a substantial amount of the unreacted corresponding carbazole. Since the unreacted carbazole (i.e., N-alkylcarbazole or N-arylcarbazole) is a photoconductor, the entire reaction product can be coated as a photoconductive layer without having to go through cumbersome purification procedures. This advantage makes the preparation and use of the herein described sensitizing dyes very attractive. A typical preparation is set forth below.

EXAMPLE 5 Oxalyl chloride (0.1 mole) is added with stirring at room temperature to a solution of N-methylcarbazole (0.1 mole) in dry methylene chloride (400 ml.) containing finely ground zinc chloride (0.2 mole). The mixture is refluxed on a steam bath for 44 hours. The product is poured into ice water (200 ml.) containing hydrochloric acid (5 ml.) and stirred for 1 hour. After filtration, the supernatent liquid is washed repeatedly with water until it is pale blue. The methylene chloride is distilled off and the product recovered. It has a melting point of 83-85 C. About to percent of this product is found to be a mixture of N-methylcarbazole (about 90 percent) and tris(4-methylcarbazol-3-yl) methane chloride salt (about 3 percent). Each component is isolated by chromatography on activated alumina.

EXAMPLE 6 Example 1 is repeated except that both the sensitizer and photoconductor are replaced with the product mixture of Example 5. A good reproduction is obtained when the exposed element is developed. 9

The invention has been described in detail with particular reference to preferred embodiments thereof, but, it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

1 claim:

1. An electrophotographic element comprising a support having coated thereon a layer of a photoconductive composition comprising a polymeric film-forming binder, a photoconductor and a sensitizer selected from the group consisting of a tris(9-alkylcarbazol-3-yl) methane dye salt and a tris(9-arylcarbazol-3-yl)Methane dye salt.

2. The element of claim 1 wherein the photoconductor is an organic photoconductor.

3. An electrophotographic element comprising a support having coated thereon a layer of a photoconductive composition comprising a polymeric film-forming binder, an organic photoconductor and a sensitizer having the formula:

fl t N R X wherein R is selected from the group consisting of an alkyl group and an aryl group,

R is selected from the group consisting of an alkoxy group, an aryloxy group, an alkyl group, a hydrogen atom, an acyl group and a halogen atom and X is an anion.

4. The element of claim 3 wherein R is an alkyl group.

5. The element of claim 3 wherein R is an aryl group.

6. The element of claim 3 wherein the organic photoconductor is selected from the group consisting of an N-arylcarbazole and an N-alkylcarbazole.

7. An electrophotographic element comprising a support having coated thereon a layer of a photoconductive composition comprising:

a. from about 10 percent to about 60 percent by weight based on said photoconductive composition of an organic photoconductor,

b. a film-forming polymeric binder for said photoconductor and c. from about 0.005 percent to about percent by weight based on said photoconductive composition of a sensitizer comprising a tris(9-methylcarbazol-3-yl)methane dye salt.

8. The element of claim 7 wherein the organic photoconductor is an N-methyl carbazole.

9. An electrophotographic element comprising a support having coated thereon a layer of a photoconductive composition comprising:

a. from about 10 percent to about 60 percent by weight based on said photoconductive composition of an organic photoconductor,

b. a film-forming polymeric and c. from about 0.005 percent to about 5 percent by weight based on said photoconductive composition of a sensitizer comprising a tris(9-ethylcarbazol-3-yl)methane binder for said photoconductor dye salt.

10. The element of claim 9 wherein the organic photoconductor is an N-ethyl carbazole.

11. A photoconductive composition comprising a photoconductor and a sensitizer selected from the group consisting of a tris(9-alkylcarbazol-3-yl)methane dye salt and a tris(9-arylcarbazol-3-yl)methane dye salt.

12. The composition of claim 11 wherein the photoconductor is an organic photoconductor.

13. The composition of claim 11 further comprising a polymeric film-forming binder for said photoconductor and said sensitizer.

14. A photoconductive composition comprising an N-substituted carbazole photoconductor and a sensitizer selected from the group consisting of a tris(9-alkylcarbazol-3- yl)methane dye salt and a tris(9-arylcarbazol-3-yl)methane dye salt.

15. in an electrophotographic process where an electrostatic charge pattern is formed on an electrophotographic element, the improvement characterized in that said photoconductive element has a photoconductive layer comprising a photoconductor and a sensitizer selected from the group consisting of a tris(9-alkylcarbazol-3-yl)methane dye salt and a tris(9-arylcarbazol-3-yl)methane dye salt. 

2. The element of claim 1 wherein the photoconductor is an organic photoconductor.
 3. An electrophotographic element comprising a support having coated thereon a layer of a photoconductive composition comprising a polymeric film-forming binder, an organic photoconductor and a sensitizer having the formula:
 4. The element of claim 3 wherein R1 is an alkyl group.
 5. The element of claim 3 wherein R1 is an aryl group.
 6. The element of claim 3 wherein the organic photoconductor is selected from the group consisting of an N-arylcarbazole and an N-alkylcarbazole.
 7. An electrophotographic element comprising a support having coated thereon a layer of a photoconductive composition comprising: a. from about 10 percent to about 60 percent by weight based on said photoconductive composition of an organic photoconductor, b. a film-forming polymeric binder for said photoconductor and c. from about 0.005 percent to about 5 percent by weight based on said photoconductive composition of a sensitizer comprising a tris(9-methylcarbazol-3-yl)methane dye salt.
 8. The element of claim 7 wherein the organic photoconductor is an N-methyl carbazole.
 9. An electrophotographic element comprising a support having coated thereon a layer of a photoconductive composition comprising: a. from about 10 percent to about 60 percent by weight based on said photoconductive composition of an organic photoconductor, b. a film-forming polymeric binder for said photoconductor and c. from about 0.005 percent to about 5 percent by weight based on said photoconductive composition of a sensitizer comprising a tris(9-ethylcarbazol-3-yl)methane dye salt.
 10. The element of claim 9 wherein the organic photoconductor is an N-ethyl carbazole.
 11. A photoconductive composition comprising a photoconductor and a sensitizer selected from the group consisting of a tris(9-alkylcarbazol-3-yl)methane dye salt and a tris(9-arylcarbazol-3-yl)methane dye salt.
 12. The composition of claim 11 wherein the photoconductor is an organic photoconductor.
 13. The composition of claim 11 further comprising a polymeric film-forming binder for said photoconductor and said sensitizer.
 14. A photoconductive composition comprising an N-substituted carbazole photoconductor and a sensitizer selected from the group consisting of a tris(9-alkylcarbazol-3-yl)methane dye salt and a tris(9-arylcarbazol-3-yl)methane dye salt.
 15. In an electrophotographic process where an electrostatic charge pattern is formed on an electrophotographic element, the improvement characterized in that said photoconductive element has a photoconductive layer comprising a photoconductor and a sensitizer selected from the group consisting of a tris(9-alkylcarbazol-3-yl)methane dye salt and a tris(9-arylcarbazol-3-yl)methane dye salt. 